Generalized Spatial Modulation for Multi-User in Visible Light Communication

In this paper, we analyzed the generalized spatial modulation (generalized SM) transmission technique for multi user indoor visible light communication (VLC) system. In generalized SM, number of bits conveyed per transmitter includes modulation symbol bits and active transmitter indices bits. Block diagonalization (BD) precoding technique is used to avoid multi user interference (MUI) in the transmitter without interference between photodiodes of the same user resulting in the noise reduction. A comparison is performed between the generalized SM with conventional Multiple Input Multiple Output (MIMO), spatial multiplexing (SMP) MIMO and spatial modulation MIMO transmission technique for multi user VLC system with regard to bit error rate (BER) performance using simulation. Simulation results show that generalized SM MIMO technique offers better signal to noise ratio (SNR) than SM MIMO by 2 dB, SMP MIMO by 5 dB and conventional MIMO technique by 8.5 dB to achieve the same BER of 10(-6). We also analyzed the influence of field of view (FOV) at an optical receiver on SNR performance with respect to single light emitting diode (LED) power.